The determination of the presence and magnitude of electromagnetic radiation or whether an object of interest is being irradiated by electromagnetic radiation generally requires an absorbing sensor and electronic circuitry that is coupled to the object being considered. Typically, most systems for detecting electromagnetic radiation require that there be some defined relation between the dimensions of the sensor and the wavelength of the electromagnetic energy that is desired to be detected. However, there are some applications where it would be inconvenient to couple the sensor and electronic circuitry to the object. For example, for electromagnetic energy propagating inside radio frequency (“RF”) waveguides in a radar or communication system, a “T-shaped” waveguide must be inserted to extract a portion of the electromagnetic radiation to an absorbing sensor. Such a sensor and method are intrusive and not amenable with system maintenance or non-invasive in-situ performance monitoring. Alternative conventional techniques further require wire penetration through the RF waveguide to a sensor. Therefore, a need exists for a system and method for determining the presence and magnitude of electromagnetic radiation or whether an object is being irradiated by electromagnetic energy that does not require intrusion of the sensor within the propagating medium such as a waveguide.